<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <script src="./jquery-3.7.1.min.js"></script>
</head>

<body>
    <div id="root">
        <p>分割线</p>
    </div>

    <script>
        //在一个元素尾部添加内容

        $("#root").append("<p> Hello World </p>")
    </script>
</body>

</html>